Laboratory animals are used extensively in biomedical research that has either direct or indirect application to human health. The nutritional appropriateness and adequacy of the diets being fed to laboratory animals have been recognized as important factors in the response of the animal to a treatment or experimental procedure. Even subtle differences in the nutrient or ingredient content of a diet can result in changes in growth, reproduction, behavior patterns, nutrient storage, enzyme activity, and tissue composition. Unrecognized dietary differences can thus result in erroneous experimental conclusions and make it difficult to reproduce results and compare data among several different laboratories. The Board on Agriculture's Committee on Animal Nutrition has recognized the importance of providing adequate diets to animals used in research and has provided leadership in this area by preparing and updating the Nutrient Requirements of Laboratory Animals. Much new information has been published since the last revision of this report in 1978. In order to provide up-to-date information, the Committee on Animal Nutrition plans to convene a subcommittee of 15 scientists with expertise in the amino acid, energy, fatty acid, mineral, and vitamin requirements of laboratory rats, mice, guinea pigs, and hamsters. The subcommittee will thoroughly review the world literature on these species and other species the subcommittee feels is important, such as the vole, ferret, and gerbil, and prepare a revision of the 1978 report. In order to provide a guide for those who are not nutritionists, the subcommittee, in consultation with AIN, will provide recommendations for the ingredient composition of natural and purified diets for growth and long-term maintenance of laboratory animals. In order to complete the revision, it is anticipated the subcommittee will hold four meetings over the 30-month period. Also, a workshop may be held in conjunction with an appropriate scientific meeting to assist members in gathering information and identifying changes in the requirements and dietary formulations. The staff officer will assist the subcommittee in all phases of the report. The report will be subject to NRC review procedures and will be distributed to the public by the National Academy Press.